Strong Correlation and Anticorrelation via Phase-Dependent Coherent Population Trapping

We present the phase control of photon correlations in a driven four-level system in the double lambda configuration. The strong correlation and the anticorrelation are. obtained when the collective phase of four applied laser fields is varied. The coherent control is based on the phase-dependent coherent population trapping （CPT）. The strong correlation occurs when the system operates near CPT, while the anticorrelation occurs when the system is far away from CPT.